Systems and methods for exploiting ADS-B frequency of arrival for flight surveillance, cyber security and meteorology

Abstract

A system is disclosed for exploiting a transmitted signal from an aircraft to determine characteristics of any of the aircraft's motion or meteorological conditions in which the aircraft is moving. The system includes a plurality of platforms for detecting Doppler shift information of the transmitted signal at each of the plurality of platforms, and a processing system for determining characteristics of any of the aircraft's motion or meteorological conditions in which the aircraft is moving.

What is claimed is: 
     
       1. A method for exploiting a transmitted signal from an aerial vehicle, said method comprising the steps of:
 receiving N frequency of arrival (FOA) signals from N collectors that detect transmission signals from an aerial vehicle during flight, the N collectors being geographically dispersed at different ranges above and below the aerial vehicle, and N being equal to at least four; 
 measuring N- 1  frequency difference of arrival (FDOA) signals based on the N FOA signals provided by N- 1  collector pairs to reduce an unknown frequency bias and noise associated with the transmission signals from the aerial vehicle; and 
 estimating a three-dimensional (3D) trajectory of the aerial vehicle based on the measured N- 1  FDOA signals, 
 wherein each of the FDOA signals is measured by:
 estimating a transit time difference from the aerial vehicle to each of a first collector and a second collector in a collector pair based on known positions of the first collector and the second collector and an estimated position of the aerial vehicle; 
 time aligning the FOA signals received from the first collector and the second collector by delaying a first received one of the FOA signals by the transit time difference; and 
 determining the FDOA signal for the collector pair by subtracting the time aligned FOA signals from each other; and 
 
 wherein each of the foregoing steps are performed in real time during flight of the aerial vehicle. 
 
     
     
       2. The method as recited in  claim 1 , wherein the transmission signals from the aerial vehicle include automated dependent surveillance broadcast (ADS-B) signals. 
     
     
       3. The method as recited in  claim 1 , wherein the N collectors that are geographically dispersed at different ranges from the aerial vehicle include one or more spacecraft-based collectors above the aerial vehicle and one or more ground-based collectors below the aerial vehicle. 
     
     
       4. The method as recited in  claim 3 , wherein the N collectors that are geographically dispersed at different ranges from the aerial vehicle further include one or more airborne collectors. 
     
     
       5. The method as recited in  claim 1 , wherein estimating the 3D trajectory of the aerial vehicle based on the measured N- 1  FDOA signals includes estimating a 3D position and velocity vector of the aerial vehicle. 
     
     
       6. The method as recited in  claim 1 , further comprising determining the estimated position of the aerial vehicle at an intersection of a plurality of geometric field of views associated with antennae of the N collectors. 
     
     
       7. The method as recited in  claim 6 , wherein the intersection provides a curved geometric surface from which a centroid location is selected as the estimated. 
     
     
       8. The method as recited in  claim 1 , wherein the first collector in the collector pair is a spacecraft-based collector above the aerial vehicle and the second collector in the collector pair is a ground-based collector below the aerial vehicle.